Devices, systems and methods for three-dimensional printing

ABSTRACT

The present disclosure provides a printer system based on high power, high brightness visible laser source for improved resolution and printing speeds. Visible laser devices based on high power visible laser diodes can be scaled using the stimulated Raman scattering process to create a high power, high brightness visible laser source.

CROSS-REFERENCE

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/817,311, filed Apr. 29, 2013, which is entirely incorporatedherein by reference.

BACKGROUND

Three-dimensional (3D) printing is a manufacturing process of making athree-dimensional solid object from a digital model. 3D printing istypically achieved using an additive process, where successive layers ofmaterial are laid down in different shapes. 3D printing is distinct fromtraditional machining techniques, which may rely on the removal ofmaterial by methods such as cutting or drilling (subtractive processes).

Various additive processes are currently available. They differ in theway layers are deposited to create parts and in the materials that canbe used. Some methods melt or soften material to produce the layers,e.g. selective laser melting (SLM) or direct metal laser sintering(DMLS), selective laser sintering (SLS), fused deposition modeling(FDM), while others cure liquid materials using different sophisticatedtechnologies, e.g., stereolithography (SLA). With laminated objectmanufacturing (LOM), thin layers are cut to shape and joined together(e.g., paper, polymer, metal).

While such approaches provide for the formation of 3D objects, there arelimitations associated with such approaches. Such approaches typicallyuse laser light with wavelengths in the infrared (IR) portion of theelectromagnetic spectrum—e.g., wavelengths greater than 1 micrometer.This may make it difficult to form objects at submicron resolution. Inaddition, typical 3D printing systems are slow and are incapable ofgenerating objects with low surface roughness, which makes such 3Dprinted objects unsuitable for numerous end uses.

SUMMARY

Recognized herein is the need for improved three-dimensional (also “3D”and “3-D” herein) printing systems and methods. In particular, there isthe need to address the slow manufacturing speed, low feature resolutionand high surface roughness of the part, as may be the case with the useof infrared (IR) lasers to manufacture components on a layer by layerbasis. The present invention addresses these and other needs, byproviding the manufacture, devices and processes taught herein.

The present disclosure provides methods, devices and systems for thefabrication of parts or components by fusing a layer of material with avisible laser system to achieve a high volumetric build rate with highresolution. Devices and systems of the present disclosure employ the useof visible lasers for three-dimensional printing applications. Devicesand systems provided herein can simultaneously or substantiallysimultaneously achieve the resolution and build rates required for usinga laser based 3D printer in production.

The present disclosure provides a three-dimensional printing system thatuses a visible laser source to produce a substantially small spot sizefor a given final focusing optic.

A 3-D laser sintering system or 3-D laser printing system uses a pair ofscanners, which can be a mechanical stepping device, a galvanometer or asimilar mechanism for scanning the angle of incidence on the finalfocusing objective to produce a translation of the laser beam in thefocal plane of the objective lens. The objective lens can be an f-thetalens or similar multi-element lens design which can produce a consistentlaser spot size over the printing plane. The spot size on the printingplane can be determined by the diameter of the collimated laser beam,the focal length of the objective lens and the wavelength of the lasersource. Thus, the wavelength of the laser source is an importantparameter in the system because it ultimately defines the minimum spotsize and the volume that can be scanned.

The print plane can be a bed of powder metal, a photopolymer that can becured or a polymer that can be flowed or cured with the application ofheat. A layer of powder can be pre-placed with a roller or blade typesystem, or through direct deposition using a powder delivery nozzle thatis coaxial with the laser beam but delivered around the periphery of thebeam.

There are at least two methods for generating high power, highbrightness laser sources operating in the visible regime: 1) frequencydoubling of an infrared laser source in a non-linear crystal such aspotassium titanyl phosphate (KTP) or periodically poled Lithium Niobate(LiNbO₃), or 2) upconversion operation of a fiber laser, where multipleinfrared photons are absorbed by a rare earth ion, such as erbium (Er)or thulium (Tm), resulting in a high energy state being populated andleading to oscillation at a visible wavelength, such as green for erbiumand blue for thulium. The frequency doubling of an infrared laser may bedifficult to scale up to high power levels because of the low damagethreshold of the KTP or lithium niobate crystals used in the doublingprocess. Consequently, lasers based on doubling techniques may belimited to less than 200 Watts with a single mode output. The secondtechnique, upconversion in a fiber laser may also be limited in outputpower because of the tendency of the fibers to suffer color centerformation due to the high energy photons present in the doped fiber. Inaddition, there are higher lying states in these upconversion layerswhich may be populated and may produce UV photons, which may lead to theformation of even more rapid color centers, which are broad bandabsorption centers formed in the fiber by the high energy of the photonsresulting in the losses in the fiber exceeding the potential gainproduced by the upconversion process and prohibiting laser operation.

The present disclosure provides devices, systems and methods forgenerating high power, high brightness visible laser radiation. Suchdevices and systems can include multiple modules, each configured toperform a given function. In some embodiments, a device for generatingvisible laser radiation comprises an array of visible laser diodes, abeam forming system and a beam convertor that uses stimulated Ramanscattering (SRS) to combine the outputs of the individual laser diodesinto a single mode output. The outputs of the visible laser diodes canbe concentrated into a fiber sufficiently small in diameter to generategain from the SRS process to enable laser operation on the first Ramanorder shifted wavelength.

Moreover, there is provided a visible diode laser system comprising amodular plate design with each laser diode mounted in a TO56 case, acollimating optic, a beam circularizing optic for making the divergenceof the collimated source symmetric, a beam shaping optical system thatcompresses an array of beamlets to eliminate dead space between each ofthe individual laser sources, and a module for interlacing each of thebeams from the modular plate. If the laser diode is collimated in oneaxis, then a cylindrical lens may be used to collimate the other axis tomake the divergence of both axes either equal or not equal, depending onthe spot that needs to be created with the final focusing optic.

The laser beams from each plate of laser diodes may be verticallyinterlaced to fill the empty space due to the mechanical properties ofthe system prior to launch into the final beam focusing optic. As usedherein, unless specified otherwise, interlace refers to placing a beamfrom different sources adjacent to each other and alternating the sourcefrom which the beams emerge when the two sources are aligned eithervertically or horizontally, so as to eliminate the dead space betweenthe beams prior to launching into a downstream (in some cases final)optic of the system. In some situations, the beam focusing optic can bea best form lens, a multi-element lens corrected for sphericalaberrations, an achromatic lens for compensating for any chromaticaberrations, or an asphere with a low f-number (or focal ratio) toenable a large collection aperture for focusing into an optical fiber.As used herein, unless specified otherwise, an asphere is a lens with anon-spherical profile defined by a Zernike polynomial to equalize thepath length of all rays passing through the aperture of the lensregardless of the position in the aperture.

Additionally, there is provided an optical fiber with triple claddingfor collecting optical pump light from the laser diode array, a low loss(e.g., less than 50 decibels/kilometer (db/km), 40 db/km, 30 db/km, 20db/km, or 10 db/km) cladding for propagating the incoherent pumpradiation from the visible laser diodes and a low loss single mode core(e.g., less than 50 db/km, 40 db/km, 30 db/km, 20 db/km, or 10 db/km).The visible laser diode radiation can be confined in the outer claddingbut randomly transverses the central core to create gain in the corethrough the SRS process. At a sufficient intensity for the visible laserdiodes, the gain may exceed the losses in the fiber, and when combinedwith feedback from either external mirrors, embedded gratings orexternal gratings, can be made to oscillate on a single transverse modewith multi-axial or single-axial mode operation. This technique may nothave been realized in the past because of the high loss (e.g., greaterthan or equal to about 50 dB/km) typical of most optical fibers in thevisible spectrum. Optical fibers of the present disclosure mayadvantageously minimize Rayleigh scattering in the fiber to enable SRSgain to exceed the losses in the optical fiber.

Additionally the present disclosure provides a method of performing ahigh power laser operation on a target material to fuse the materialtogether, to cure the materials or to ablate the material, which can beused to form a multilayered 3D object. The material can be any of anumber of materials, such as a metallic material, insulating material,semiconducting material, polymeric material, a composite material, or acombination thereof. Example materials include, without limitation,steel, titanium, copper, bronze, gold, and alloys of these materials.

The absorption characteristics of materials can increase with decreasingwavelength. As a consequence, there may be a significant increase in theprocessing speed when using a blue laser wavelength compared to an IRlaser (see Table 1 below).

TABLE 1 Absorption Processing Speed Advantage Aluminum Steel Copper GoldAluminum Steel Copper Gold Laser System (Al) (St) (Cu) (Au) Ni (Al) (St)(Cu) (Au) Ni Blue Laser 32% 67% 58% 60% 65% 200% 129% 967% 3000% 144%Fiber Laser 16% 52%  6%  2% 45%

An aspect of the present disclosure provides a printing system forforming a three-dimensional object, comprising a laser light source thatgenerates a coherent beam of visible light by stimulated Ramanscattering, a substrate in optical communication with the laser lightsource, and a scanning module downstream of the laser light source. Thescanning module can be adapted to generate a scanning motion of thecoherent beam of visible light with respect to the substrate, whichscanning motion corresponds to a predetermined shape of thethree-dimensional object. The printing system can further comprise acomputer control system operatively coupled to the laser light sourceand the scanning module. The computer control system can be programmedto (i) control the scanning motion in a predetermined manner and (ii)modulate a power of the laser light source, to form the object from thesubstrate.

Another aspect of the present disclosure provides a printing system forforming a three-dimensional object, comprising a laser light source thatcomprises at least one optical fiber that outputs a coherent beam ofvisible light in the optical fiber with a Rayleigh loss that is lessthan about 50 decibels per kilometer (db/km), a substrate (e.g., powder)in optical communication with the laser light source, and a scanningmodule downstream of the laser light source, wherein the scanning moduleis adapted to generate a predetermined scanning motion of the beam ofvisible light with respect to the substrate. The predetermined scanningmotion can correspond to a shape of the three-dimensional object. Theprinting system can further comprise a computer control systemoperatively coupled to the laser light source and the scanning module.The computer control system can be programmed to (i) control thescanning motion in a predetermined manner and (ii) modulate a power ofthe laser light source, to form the object from the substrate.

Another aspect of the present disclosure provides a method for forming athree-dimensional object, comprising providing a laser light source anda scanning module optically downstream of the laser light source, andusing the laser light source, generating a coherent beam of visiblelight by stimulated Raman scattering. Next, the coherent beam of visiblelight is directed to a substrate that is in optical communication withthe laser light source. A feature is then generated in or from thesubstrate. The feature can correspond to at least a portion of apredetermined shape of the three-dimensional object. Next, the scanningmodule is used to generate a scanning motion of the coherent beam ofvisible light with respect to the substrate. The scanning motion cancorrespond to the predetermined shape of the three-dimensional object.The substrate is then moved relative to the laser light source along adirection that is generally parallel to the coherent beam of visiblelight.

Another aspect of the present disclosure provides a computer-readablemedium (e.g., memory) comprising machine executable code that, uponexecution by the one or more computer processors, implements any of themethods above and elsewhere herein.

Another aspect of the present disclosure provides a computer systemcomprising one or more computer processors and memory coupled thereto.The memory comprises machine executable code that, upon execution by theone or more computer processors, implements any of the methods above andelsewhere herein.

Additional aspects and advantages of the present disclosure will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein only illustrative embodiments of thepresent disclosure are shown and described. As will be realized, thepresent disclosure is capable of other and different embodiments, andits several details are capable of modifications in various obviousrespects, all without departing from the disclosure. Accordingly, thedrawings and description are to be regarded as illustrative in nature,and not as restrictive.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings (also “figure” and “FIG.” herein), of which:

FIG. 1 is a schematic view of an embodiment of a three-dimensional (also“3-D” and “3D” herein) printing system based on scanners and an f-thetalens using a visible laser source;

FIG. 2. Is a schematic view of an embodiment of a 3-D printing systemusing linear translation stages with a visible laser source;

FIG. 3 is a schematic view of an embodiment of a visible laser source;

FIG. 4 is a view of an embodiment of a modular laser plate usingmultiple laser diode sources packaged in a TO56 package;

FIG. 5 is a view of an embodiment of multiple modular laser platesstacked to form a two dimensional array of laser sources;

FIGS. 6A-6B schematically illustrate the evolution of pump power into asingle mode output; and

FIG. 7 schematically illustrates a computer system that is programmed orotherwise configured to implement methods of the present disclosure.

DETAILED DESCRIPTION

While various embodiments of the invention have been shown and describedherein, it will be obvious to those skilled in the art that suchembodiments are provided by way of example only. Numerous variations,changes, and substitutions may occur to those skilled in the art withoutdeparting from the invention. It should be understood that variousalternatives to the embodiments of the invention described herein may beemployed.

The term “visible light,” as used herein, generally referselectromagnetic radiation (light) with a wavelength between about 380nanometers (nm) and 760 nm (400-790 terahertz). Visible light is visibleby the human eye. Visible laser light has a wavelength between about 380nm and 760 nm.

The term “high power laser energy,” as used herein, generally refers toa laser beam having at least about 200 Watts (W) of power.

The term “substantial power loss,” as used herein, generally refers to aloss of power that is greater than about 10 dB/km (decibel/kilometer)for the visible wavelength.

The term “visible wavelength,” as used herein, generally refers to alaser beam with a wavelength greater than 400 nm but less than 750 nm.

The term “high brightness,” as used herein, generally refers to singlemode laser operation with diffraction limited or near diffractionlimited performance.

The term “beamlet,” as used herein, generally refers to a beam ofelectromagnetic radiation from a single laser diode source that may becollimated in one axis or in two orthogonal axes.

The term “interlace,” as used herein, generally refers to placing a beamfrom different sources adjacent to each other and alternating the sourcefrom which the beams emerge when the two sources are aligned eithervertically or horizontally, so as to eliminate the dead space betweenthe beams prior to launching into a downstream (in some cases final)optic of the system.

The term “f-number” (also focal ratio, f-ratio, f-stop, and relativeaperture), as used herein, generally refers to the ratio of the focallength to the diameter of the entrance pupil of the lens of an opticalsystem.

The term “asphere,” as used herein, generally refers to a lens with anon-spherical profile defined by a Zernike polynomial to equalize thepath length of all rays passing through the aperture of the lensregardless of the position in the aperture. Zernlike polynomials are asequence of polynomials that are orthogonal on the unit disk.

The term “build volume,” as used herein, generally refers to the volumeof an object under fabrication, such as a 3D printed object, which, forexample, can be scanned by a laser beam with a lateral extent “x”, atransverse extent “y” and a vertical extent “z”. The vertical extent canbe defined by an elevator which incrementally translates the printedobject in the “z” direction after each layer is processed.

The term “single mode,” as used herein, generally refers to neardiffraction limited performance of a laser system with a low M² value,where M² defines the beam caustic and how close the laser beam comes todiffraction limited performance. As used herein, unless specifiedotherwise, M² is defined as the number of times diffraction limited thebeam is and can be equal to or greater than about 1, or greater than orequal to about 1.1 but still single transverse mode, or greater than orequal to about 1.3 but still single transverse mode.

The term “stimulated Raman scattering,” as used herein, generally refersto a process in which the photons scatter off of molecules of a fiber toeither a lower energy state (Stokes shift) or a higher energy state(Anti-Stokes shift) to create gain in the optical medium. In a laserbeam of photons, some Stokes photons may have been previously generatedby spontaneous Raman scattering (and may remain in the material), orsome Stokes photons (“signal light”) may have been deliberately injectedtogether with the original light (“pump light”). Generally, when photonsare scattered from an atom or molecule, most photons are elasticallyscattered (Rayleigh scattering), such that the scattered photons havethe same energy (frequency and wavelength) as the incident photons. Asmall fraction of the scattered photons (e.g., approximately 1 in 10million) are scattered by an excitation, with the scattered photonshaving a frequency different from, and usually lower than, that of theincident photons. In a gas, Raman scattering can occur with a change inenergy of a molecule due to a transition from one energy state toanother. The Raman-scattering process can take place spontaneously;i.e., in random time intervals, one of the many incoming photons isscattered by the material. This process may be referred to as“spontaneous Raman scattering.” In stimulated Raman scattering (also“SRS” herein), the total Raman-scattering rate can be increased beyondthat of spontaneous Raman scattering: pump photons can be converted morerapidly into additional Stokes photons. The more Stokes photons arealready present, the faster more of them are added. This can effectivelyamplify the Stokes light in the presence of the pump light, which can beexploited in Raman amplifiers and Raman lasers.

Three-Dimensional Printing Devices, Systems and Methods

The present disclosure provides devices, systems and methods forapplying directed energy to a layer of material to fuse or ablate thematerial in the creation of an object (or part) directly from a computerdesign. This can be used to generate or print a three-dimensionalobject, such as in a layer-by-layer fashion. Methods provided herein canaccomplish the consolidation of powder material into a working part, orthe fusing of a binder into a part that has to be post processed tocomplete the consolidation of the part.

Devices, systems and methods of the present disclosure can be used toform various objects or parts, such as objects for consumer orindustrial uses. Such objects can be digitally designed on a computersystem, and fabricated using devices and systems provided herein. Insome examples, devices, systems and methods of the present disclosurecan be used to form consumer parts (e.g., toys), electronics components,medical devices, or components of industrial or military equipment.Devices, systems and methods of the present disclosure can have variousapplications, such as consumer, educational, industrial, medical andmilitary applications. In an industrial setting, devices, systems andmethods provided herein can be used for material processing.

Devices, systems and methods of the present disclosure can employ theuse of visible lasers to generate objects at high precision and in atime scale that is much less than other systems currently available. Insome cases, this is based on the unexpected realization that stimulatedRaman scattering (SRS) can be used to generate a highly coherent beam ofvisible laser light in a single mode output. Such lasers can be operatedas a high resolution laser projector or a supercontinuum laser.

FIG. 1 is a schematic of the 3-D laser printing system based on a highpower visible laser system. The system includes a single mode visiblelaser source (1001). The visible laser source (1001) can include one ormore visible laser diodes. The output (1002) of the visible laser (1001)can be directed at a pair of scanners (1003) that scan the beam inorthogonal directions. The scanners (1003) can be a pair ofgalvanometers which scan the laser beam across the focal plane in eitheran X-Y raster pattern or a vector scanning pattern. The scanners (1003)can create an angular deviation from orthogonal, which can produce atranslation of the laser spot in the focal plane. Laser emissionreflected (1004) by the scanners (1003) can be directed to an objectivelens (1005), which generates a focused beam (1006) that can be directedto a substrate (1007), such as a powder. In some examples, the substrate(1007) is a powder in a powder bed. This can melt or fuse the substrate(1007) at the focal point of the laser beam.

The scanners (1003) can be used to raster the laser emission (1004) overthe powder (1007) in a manner that defines the two-dimensional andthree-dimensional shape of a three-dimensional object under fabrication.This can be performed in a layer-by-layer fashion. At a given layer, thetwo-dimensional shape of the object in that layer is defined using thelaser emission (1004). The two-dimensional shape of the object at eachsuccessive layer can be defined using the laser emission (1004) togenerate the overall 3-D shape of the object.

Various parameters of the laser emission (1004) can be selected toprovide a desired shape of the object. Such parameters include, withoutlimitation, exposure time and laser power. For example, the time thatthe substrate (1007) is exposed to the laser emission (1004) can beselected based on a melt or fuse rate of the material of the substrate(1007).

The substrate (1007) can be supported by or on a substrate holder. Thesubstrate holder can include a vertical translator (“Z-axis translator,”as shown in FIG. 1) (1008) to move the object vertically (i.e., parallelto the general direction of propagation of laser light) duringlayer-by-layer fabrication or growth of the object. The verticaltranslator can be a motor, such as a step motor. The vertical translator(or elevator) can step the substrate in increments of at least about 5nanometers (nm), 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 200 nm, 300nm, 400 nm, 500 nm, 1 micrometer (μm), 2 μm, 3 μm, 4 μm, 5 μm, 10 μm, 20μm, 30 μm, 40 μm, or 50 μm during fabrication of the object.

As an alternative, or in addition to, an assembly (e.g., TO56 case)comprising visible laser (1001), scanners (1003) and objective lens(1005) can be moved vertically with respect to the substrate (1007). Theassembly can include a vertical translator that can step the assembly inincrements of at least about 5 nanometers (nm), 10 nm, 20 nm, 30 nm, 40nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 1 micrometer (μm), 2μm, 3 μm, 4 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm duringfabrication of the object.

The diameter of the laser spot formed in FIG. 1 can be determined by thefocal length of the objective lens (1005), the beam size on theobjective lens (1005) and the wavelength of the laser beam. The buildvolume may be limited by the diameter of the objective lens and the sizeof the beam on the objective including the translations due to thescanners. The spot size in an IR based system is approximately 70micrometers (μm) with a build volume of 9.6″×9.6″×11″ (Table 2) due tothe finite size of the beam on the objective lens. A blue laser systemwith a wavelength of 459 nm can advantageously create a spot size thatis less than or equal to about 35 μm, in some cases with the sameoptical system as the IR system. Since the optical system can be thesame, the build volume remains unchanged but the resolution and surfacequality is improved by better than a factor of 1, 1.1, 1.2, 1.3, 1.4,1.5, 2. 3, 4, 5, 6, 7, 8, 9, or 10. If the blue laser system based 3-Dprinter final focusing lens is changed to produce a 70 μm spot, then thesame resolution is achieved as the IR system, but now the build volumecan be increased by a factor of 150×.

TABLE 2 Current IR Blue Laser Performance Laser System Power 2000 W 1000W Print Speed 20 cc/hr 50 cc/hr Resolution 70 um 70 um Build Volume 9.8″× 9.8″ × 11″ 53″ × 53″ × 55″ Surface Finish ~2Ra ~2Ra

Alternatively looking at FIG. 2, a 3-D printer in this embodiment isbased on a pair of linear translation stages instead of scanners forprinting the pattern. The linear translation stages change thefundamental geometry governing the spot size and the writing speed andopens up the ability to use a sufficiently short focal length lens suchthat the spot size is less than 1000 nanometers (nm), 900 nm, 800 nm,700 nm, 600 nm, or 500 nm. This sub-micron spot size may be suitable forthe direct manufacture of Micro-Electrical-Mechanical (MEMS) devices.The laser beams (2002, 2004 and 2006) can be translated across thesurface of a substrate (e.g., powder) using a translation stage (2007)to directly write a pattern in either a substrate or with the directinjection of the substrate into the beam with a coaxial nozzle. Theresolution of the part can be the result of the small diameter beam andthe size of the substrate, such as the nanometer scale powder (e.g., 50nm) used to directly write the part.

The translation stage (2007) can enable the substrate to be translatedin an X-Y plane (orthogonal to the general direction of propagation oflaser light), and/or along a Z-axis, which may be parallel to thegeneral direction of propagation of laser light. The translation stage(2007) can include two linear sub-stages. The translation stage (2007)can be part of a substrate holder, which can be configured to supportthe substrate during fabrication of the object. A translation stage caninclude a motor, such as a step motor. The translation stage (2007) caninclude a vertical translator (2008) that can translate the stage alongthe Z-axis during fabrication. The vertical translator (or elevator) canstep the substrate in increments of at least about 5 nanometers (nm), 10nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm,1 micrometer (μm), 2 μm, 3 μm, 4 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm,or 50 μm during fabrication.

As an alternative, or in addition to, an assembly comprising visiblelaser (2001), x-y alignment system (2003) and objective lens (2005) canbe moved vertically with respect to the substrate, which may be situatedat the stage (2007). The assembly can include a vertical translator thatcan step the assembly in increments of at least about 5 nanometers (nm),10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500nm, 1 micrometer (μm), 2 μm, 3 μm, 4 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40μm, or 50 μm during fabrication of the object.

In some embodiments, the laser (2001) and objective lens (2002-2005) aretranslated as a subsystem across the substrate as the power in the beamis modulated, thereby defining the part layer by layer. The laser (2001)can be a single mode visible laser. The laser (2001) can include one ormore visible laser diodes. For example, the power in the beam ismodulated by turning laser power on or off, or increasing and decreasinglaser power in a manner that is predetermined based on the shape of thepart (or object) being fabricated. As an alternative, the laser can bestationary, and an optical head is translated across the part takingadvantage of the highly collimated nature of the laser beam. Such flyingoptic head technique may include components as currently used in CO₂flat sheet bed cutters. See, e.g., Todd, Robert H.; Allen, Dell K.;Alting, Leo (1994). Manufacturing Processes Reference Guide. IndustrialPress Inc. ISBN 0-8311-3049-0, which is entirely incorporated herein byreference.

The speed of fabrication or manufacturing can be improved in manysystems today with a laser capable of being modulated at a much higherrate than today's fiber lasers. When writing an object (or part), thescanning speed and the laser power can determine how fast the beam canbe moved for a given material. However, as the laser beam is movedacross a substrate (e.g., powder in a power bed), it may be necessary toturn the laser off when there is not supposed to be any structurepresent in the part at the particular point in the layer being printed.The faster the beam is scanned across the substrate surface and thesmaller the feature size, the faster the laser beam has to be turned onand off. The laser described in this application is capable of beingmodulated at substantially high modulation rates. The substantially highmodulation rate can improve the surface characteristics (e.g.,roughness) of the part being manufactured as well as enable very highspatial resolution components to be manufactured.

Infrared (IR) lasers used today may be limited to a modulation rate of50 kHz (1 kHz=1000 cycles per second). However, visible light laser(e.g., blue laser) based devices and systems of the present disclosureare capable of being modulated at rates greater than or equal to about50 kHz, 100 kHz, 200 kHz, 300 kHz, 400 kHz, 500 kHz, 1 GHz (1 GHz=1000kHz), 2 GHz, 3 GHz, 4 GHz, 5 GHz, or 10 GHz. To achieve production rateswith this type of a system, multiple devices can be processed inparallel with the same laser system using a high speed beam sharingswitch or with parallel laser systems synchronized to the motion system.An example switch is a multi-port beam switch, such as, for example, amulti-port beam switch comprising 2, 3, 4, 5 or 6 channels.

Visible light laser based devices and systems of the present disclosurecan be used to form objects (or parts) having substantially smoothsurfaces. In some cases, the surface roughness of an object (or part)formed using devices and systems of the present disclosure can bebetween about 0.1 nm and 50 nm, or 1 nm and 20 nm, or 1 nm and 10 nm, asmeasured by transmission electron microscopy (TEM).

Visible light laser based devices and systems of the present disclosurecan be used to form objects (or parts) having substantially high aspectratios (e.g., length divided by width). In some cases, the aspect ratioof a feature in an object (or part) formed using devices and systems ofthe present disclosure may be at least about 1.1:1, 1.2:1, 1.3:1, 1.4:1,1.5:1, or 2:1, or 5:1, or 10:1, or 20:1, 50:1, 100:1 or more.

Device and systems of the present disclosure can employ visible lasersources scaled to high power and high brightness. A high power lasersource can have a power greater than about 100 Watts, or greater thanabout 200 Watts, or greater than about 300 Watts, or greater than about400 Watts, or greater than about 500 Watts, or greater than about 1,000Watts, or greater than about 2,000 Watts. Laser sources of the presentdisclosure can operate in single mode, which can include neardiffraction limited performance from the laser system with a low M²value, where M² defines the beam caustic and how close the laser beamcomes to diffraction limited performance. As used herein, unlessspecified otherwise, M² is defined as the number of times diffractionlimited the beam is and can be equal to or greater than about 1, greaterthan or equal to about 1.1 but still single transverse mode, or greaterthan or equal to about 1.3 but still single transverse mode.

FIG. 3 shows a high power, single mode visible laser source (3000), inaccordance with some embodiments of the invention. The laser (3000)includes an array of high power, high brightness visible laser diodes(3001). Visible laser light from the diodes (3001) can be collimated andshaped into a beam by a beam combination and shaping optic assembly(3002) to match the numerical aperture and spot requirements of a Ramanconvertor fiber or resonator (3010), which comprises a high reflectivity(HR) back mirror (3003), a low loss optical fiber (3004) and a lowerreflectivity output coupler (3005). The Raman convertor (3010) convertsthe power from the plurality of visible laser diodes arranged in alinear or two dimensional array into a single coherent laser beam (3006)using a non-linear approach, such as stimulated Raman scattering (SRS).

In an example, the back mirror (3003) can be a high reflectivity elementand the output coupler (3005) can be a cleaved or polished facet withthe appropriate dielectric coating. In another example, the back mirror(3003) is a high reflectivity element and the output coupler (3005) is agrating. In another example, the back mirror (3003) is a highreflectivity element and the output coupler (3005) is an embedded FiberBragg Grating (FBG). In another example, the back mirror (3003) is anembedded FBG designed to have high reflectivity for the lowest orderTEM_(∞) mode and the output coupler (3005) is a cleaved or polishedfacet with the appropriate dielectric coating. In another example, theback mirror (3003) is an embedded FBG designed to have high reflectivityfor the lowest order TEM_(∞) mode and the output coupler (3005) is agrating. In another example, the back mirror (3003) is an externalVolume Bragg Grating (VBG) and the output coupler (3005) is a cleaved orpolished facet with the appropriate dielectric coating. In anotherexample, the back mirror (3003) is a high reflectivity element and theoutput coupler (3005) is a lower reflectivity embedded FBG. In anotherexample, the back mirror (3003) is an embedded FBG and the outputcoupler (3005) is a low reflectivity mirror. In another example, theback mirror (3003) is a VBG and the output coupler (3005) is a cleavedor polished facet with the appropriate dielectric coating. In anotherexample, the back mirror (3003) is a high reflectivity mirror and theoutput coupler (3005) is a low reflectivity VBG.

The fiber (3010) can be in optical communication with the optic assembly(3002). The fiber (3010) can include a central core that is single mode,or near single mode, a cladding of larger diameter than the core forcapturing the output of the visible laser diode array and an outercladding to guide the visible laser diode array light along the fiber.The central core may have a diameter greater than or equal to about 3μm, greater than or equal to about 5 μm, greater than or equal to about15 μm, or greater than or equal to about 25 μm. The first claddingregion may have a diameter greater than or equal to about 50 μm, greaterthan or equal to about 80 μm or greater than or equal to about 100 μm.The outer cladding region may have a diameter greater than the diameterof the inner cladding by a factor greater than or equal to about 1.1,1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 3, 4, 5, or 10. In someexamples, the outer cladding has a diameter that is greater than orequal to about 55 μm, greater than or equal to about 90 μm, or greaterthan or equal to about 110 μm. In some situations, in order to providestrength and durability, the outer cladding may have a diameter begreater than or equal to about 125 μm.

The diameter of the first cladding region may be an important parameterin the operation of the visible laser because the intensity of thevisible laser (e.g., blue laser) diode light defines the gain that canbe generated with the SRS process. The gain for a Raman fiber may bedetermined by the amount of pump power in the core of the fiber. Thepower for generating Raman gain can reside in the cladding just outsideof the core region. Since the cladding is larger in diameter than thecore, the Raman gain for the laser is significantly less than the gainthat occurs when all of the power is confined to the core. For example,a 200 Watt visible Raman laser requires the pump power from the array oflaser diodes to be able to be launched into the inner cladding regionwhich needs to be on the order of 60 μm in order to achieve sufficientgain for efficient operation. As another example, a 2,000 Watt visibleRaman laser requires a cladding diameter of 85-100 μm to achieveefficient operation, which is driven by the ability of the laser diodesthat are launched as pump diodes into the outer clad.

Visible laser diodes of the present disclosure may be capable of greaterthan about 1 Watt of output power from a narrow stripe suitable forlaunching a plurality of laser diodes into a fiber with a diameter ofless than 100 μm. Laser diode brightness is defined as the product ofthe output power, the stripe width and the divergence angle. The narrowstripe width can be greater than or equal to about 5 μm, greater than orequal to about 10 μm, greater than or equal to about 15 μm, but in somecases no greater than about 35 μm. The divergence angle in the fast axiscan be greater than or equal to about 20 degrees, greater than or equalto about 40 degrees, or greater than or equal to about 90 degrees from alaser diode. The divergence angle in the slow axis can be greater thanor equal to about 1 degree, greater than or equal to about 10 degrees,or greater than or equal to about 20 degrees. The laser diode can have afast axis divergence between about 18 and 25 degrees Full Width HalfMaximum (FWHM) and a slow axis divergence between about 12 and 15degrees FWHM. In an example, the laser diode has a fast axis divergenceof 25 degrees FWHM and a slow axis divergence of 15 degrees FWHM, whichis a source brightness of 20 MW/cm²-steradian. The source brightnessdefines the maximum number of devices which can be coupled into anoptical fiber, the higher the brightness number, the greater the numberof devices that can be coupled.

The optical fiber can be a triple clad design as described above, with asubstantially low loss in the visible wavelength range due to Rayleighscattering in both the central single mode core and the first cladding.In some cases, the laser diodes operate at 450 nm and produce gain overa 10 nm range between 451 nm and 461 nm depending on the intrinsicscattering losses in the optical fiber. The fiber can have a Rayleighscattering loss of less than 10 decibels/km (dB/km) at 459 nm which issubstantially lower than a pure silica core fiber which can have lossesgreater than or equal to 50 dB/km. The Raman gain that is generated maybe sufficient to overcome the Rayleigh losses in the fiber, if losses inthe fiber are less than about 50 dB/km, less than 40 dB/km, less than 30dB/km, less than 20 dB/km, less than 10 dB/km, less than 5 dB/km, orless than 1 dB/km. The lower the losses in the fiber, the higher theoverall efficiency of the laser.

The laser diode array can be a modular design based on plates whichcombine and condition the outputs of a linear array of laser diodes.FIG. 4 shows a laser plate that includes a linear array of high powervisible laser diodes (4001) with a collimating optic associated witheach laser diode to provide collimated sources (4004), as well as a beamshaping optical system (4003), and a set of compressing optical elements(4004) (also “beam compressor” herein) to eliminate the space betweenthe collimated laser sources in one axis.

In an example, the collimating optic is an aspheric cylindrical lensalong one axis and the beam shaping optical system (4003) is acylindrical lens in another axis. In another example, the beam shapingoptical system (4003) comprises two optical elements forming acylindrical telescope to resize one axis of the beamlet.

In some examples, a beam compressor (4004) is a turning mirror or prism.In an example, each beam compressor comprises at least one turningmirror. A turning mirror can be a prism operating in Total InternalReflection (TIR) mode. In some cases, a turning mirror is a highreflectivity dielectric coated substrate, such as, for example, adielectric coating on a fused silica substrate which can be 99%reflectivity for unpolarized light at 459 nm, or a metal mirror withenhanced reflectivity coating, such as, for example, an aluminizedmirror with an enhanced reflectivity enabling up to 92% reflection forunpolarized light at 459 nm.

In an example, a beam compressor (4004) for each plate comprises a platewith alternating high reflectivity/anti-reflectivity coatings to reflectthe beams from each plate or pass the beams from each plate. In anotherexample, a beam compressor (4004) for each plate comprises a stack ofprisms oriented to direct the beam from each laser plate to be parallelwhile minimizing the dead space between the beams from each laser plate.In another example, a beam compressor (4004) for each plate comprises aplate with alternating high reflectivity/holes in the plate to reflectthe beams from each plate or to pass the beams from each plate.

In some examples, the beam shaping optical system (4003) comprises oneor more anamorphic prims. In an example, the beam shaping optical system(4003) comprises a pair of anamorphic prims.

The compressed beamlets can make up the composite beam that reflect offof an interlacing optic (4005) into the final focusing optic (4006) todeliver the laser power to a pump fiber (4007) or directly to a laserfiber (4007). The laser fiber (4007) can be a triple clad fiber with asingle mode core or near single mode core. The laser cavity can beformed with either external mirrors, gratings or Fiber Bragg Gratings(FBG) embedded in the central core. In some embodiments, a laserresonator is based on the embedded FBGs, because the gratings have bothspectral and modal selectivity, which enables the Raman laser to operateon a single transverse mode even if the fiber core is multi-mode.

The central core can be a fused silica core which has the lowest Ramangain coefficient compared to a germanium doped core or a phosphorusdoped core. The Raman shift for the fused silica and germanium dopedcore are similar and less than about 12 nm at 450 nm, but the shift forthe phosphorus doped core is substantially greater, with up to about a75 nm shift at 450 nm. The central core can be a fused silica core tominimize the potential for color center generation in the fiber. Adopant may be added to the core to further suppress photo-darkeningeffects, and the photo-darkening may be minimized by keeping anyultraviolet (UV) components from being generated in the laser cavity. Aslong as the laser emission is confined to the Stokes scatteringcomponent, the wavelength can be longer than the pump wavelength andthere will be no UV radiation generated. The gain for the Stokes wavecan be substantially larger than for the Anti-Stokes wave, making itless likely that shorter wavelengths will be generated by Anti-Stokesscattering events.

A dopant, such as a material having hydroxyl groups (OH), may be addedto the core and the first fiber clad to suppress the Rayleigh scatteringlosses in the visible regime. The fundamental requirement of any lasersystem is that the gain in the system may exceed the losses in thesystem. While the stimulated Raman scattering can provide sufficientgain to overcome the 50 dB/km in standard optical fibers, efficientlaser operation can occur when the loss associated with Rayleighscattering is less than 50 dB/km, less than 40 dB/km, less than 30dB/km, less than 20 dB/km, less than 10 dB/km, less than 5 dB/km, orless than 1 dB/km.

Scaling the power output of the laser system can be accomplished bystacking the laser plates in FIG. 4 to form a two dimensional array oflaser diode beams. For example, the lasers can be mounted on a singlecooled plate that can be stacked to form a two dimensional source oflaser diode power. The plate can be cooled with a cooling fluid, such aswater. In some cases, cooling can be accomplished with the aid of fans,heat fins and/or a heat exchanger employing a cooling fluid.

In some situations, the laser plates are stacked with minimal spacebetween each of the beams produced by each of the plates. The laserplates can be stacked with a dead space equal to the height of the laserbeam emitted by the plate.

Referring to FIG. 5, a laser system is shown having multiple plates.Each plate has precision ground mounting point to establish the flatnessand spacing of each plate (5006). The plates can be physically heldtogether to form a stack of plates. Plates can be physically heldtogether using a mechanical fastening member (e.g., screws) or achemical fastening member (e.g., an adhesive). Each beam of a plate canbe precisely spaced to create a gap where another beam can be interlaced(5002, 5003) to minimize the dead space between the beams launching intothe lens (4006). Two arrays of lasers with complimentary spacing (5001,5007) are used with the beam from each beam plate interlaced between thebeams of the other plate. Each array can include a plurality of visiblelight laser diodes. The laser plates can be identical in design butmounted in opposite directions to enable a common platform throughoutthe system. The beam combination method (5004, 5005) can be either astack of prisms or a plate that alternatively transmits or reflects eachof the beams. The transmission part of the plate (5005) can be either ahole or an anti-reflection coated region of the plate where the plate isa material such as fused silica or a metal. The reflecting portion ofthe plate (5004) can be either a dielectric coating or an enhanced metalmirror. Alternatively, a combination method, such as a stack of prisms,can be used in either a refracting configuration or a Total InternalReflection (TIR) configuration, to alternatively combine the beams fromeach of the laser plates.

The beams created from the two dimensional array of plates can be highlycollimated and can be further combined with other two dimensional arraysof plates using either wavelength or polarization to further increasethe pump brightness. With reference to FIGS. 6A and 6B, multiple sourceswithin a wavelength bandwidth of up to 5 nm (6011, 6012) or (6021, 6022)can be used to create gain through the SRS process in a fused silicafiber (6001, 6002). The wavelength pump spectral bandwidth for aplurality of sources can be less than about 4 nm, less than 3 nm, lessthan 2 nm or less than 1 nm. A substantially wider spectral pumpbandwidth for the laser diodes can be used with a phosphorous dopedfiber because of the broader gain profile for the fiber. For the case ofa phosphorous doped fiber, the spectral pump bandwidth for a pluralityof laser sources can be less than about 35 nm, less than 25 nm, lessthan 15 nm, less than 5 nm or less than 1 nm.

Control Systems

Devices, systems and methods of the present disclosure can beimplemented using computer control systems. FIG. 7 shows a computersystem 701 that is programmed or otherwise configured to regulate theoperation of a 3D printing device, system and method of the presentdisclosure. The computer system 701 includes a central processing unit(CPU, also “processor” and “computer processor” herein) 705, which canbe a single core or multi core processor, or a plurality of processorsfor parallel processing. The computer system 701 also includes memory ormemory location 710 (e.g., random-access memory, read-only memory, flashmemory), electronic storage unit 715 (e.g., hard disk), communicationinterface 720 (e.g., network adapter) for communicating with one or moreother systems, and peripheral devices 725, such as cache, other memory,data storage and/or electronic display adapters. The memory 710, storageunit 715, interface 720 and peripheral devices 725 are in communicationwith the CPU 705 through a communication bus (solid lines), such as amotherboard. The storage unit 715 can be a data storage unit (or datarepository) for storing data. The computer system 701 can be operativelycoupled to a computer network (“network”) 730 with the aid of thecommunication interface 720. The network 730 can be the Internet, aninternet and/or extranet, or an intranet and/or extranet that is incommunication with the Internet. The network 730 in some cases is atelecommunication and/or data network. The network 730 can include oneor more computer servers, which can enable distributed computing, suchas cloud computing. The network 730, in some cases with the aid of thecomputer system 701, can implement a peer-to-peer network, which mayenable devices coupled to the computer system 701 to behave as a clientor a server.

The CPU 705 can execute a sequence of machine-readable instructions,which can be embodied in a program or software. The instructions may bestored in a memory location, such as the memory 710. Examples ofoperations performed by the CPU 705 can include fetch, decode, execute,and writeback.

The CPU 705 can be part of a circuit, such as an integrated circuit. Oneor more other components of the system 701 can be included in thecircuit. In some cases, the circuit is an application specificintegrated circuit (ASIC).

The storage unit 715 can store files, such as drivers, libraries andsaved programs. The storage unit 715 can store user data, e.g., userpreferences and user programs. The computer system 701 in some cases caninclude one or more additional data storage units that are external tothe computer system 701, such as located on a remote server that is incommunication with the computer system 701 through an intranet or theInternet.

The computer system 701 can communicate with one or more remote computersystems through the network 730. For instance, the computer system 701can communicate with a remote computer system of a user. Examples ofremote computer systems include personal computers (e.g., portable PC),slate or tablet PC's (e.g., Apple® iPad, Samsung® Galaxy Tab),telephones, Smart phones (e.g., Apple® iPhone, Android-enabled device,Blackberry®), or personal digital assistants. The user can access thecomputer system 701 via the network 730.

The computer system 701 can be in communication with a 3-D printingdevice or system 735. The computer system 701 can be in communicationwith the 3-D printing device either directly (e.g., by direct wired orwireless connectivity), or through the network 730. The 3-D printingdevice or system 735 can be any device or system described above andelsewhere herein, such as, for example, the 3-D printing laser system ofFIG. 1.

Methods as described herein can be implemented by way of machine (e.g.,computer processor) executable code stored on an electronic storagelocation of the computer system 701, such as, for example, on the memory710 or electronic storage unit 715. The machine executable or machinereadable code can be provided in the form of software. During use, thecode can be executed by the processor 705. In some cases, the code canbe retrieved from the storage unit 715 and stored on the memory 710 forready access by the processor 705. In some situations, the electronicstorage unit 715 can be precluded, and machine-executable instructionsare stored on memory 710.

The code can be pre-compiled and configured for use with a machine havea processer adapted to execute the code, or can be compiled duringruntime. The code can be supplied in a programming language that can beselected to enable the code to execute in a pre-compiled or as-compiledfashion.

Aspects of the systems and methods provided herein, such as the computersystem 701, can be embodied in programming. Various aspects of thetechnology may be thought of as “products” or “articles of manufacture”typically in the form of machine (or processor) executable code and/orassociated data that is carried on or embodied in a type of machinereadable medium. Machine-executable code can be stored on an electronicstorage unit, such memory (e.g., read-only memory, random-access memory,flash memory) or a hard disk. “Storage” type media can include any orall of the tangible memory of the computers, processors or the like, orassociated modules thereof, such as various semiconductor memories, tapedrives, disk drives and the like, which may provide non-transitorystorage at any time for the software programming. All or portions of thesoftware may at times be communicated through the Internet or variousother telecommunication networks. Such communications, for example, mayenable loading of the software from one computer or processor intoanother, for example, from a management server or host computer into thecomputer platform of an application server. Thus, another type of mediathat may bear the software elements includes optical, electrical andelectromagnetic waves, such as used across physical interfaces betweenlocal devices, through wired and optical landline networks and overvarious air-links. The physical elements that carry such waves, such aswired or wireless links, optical links or the like, also may beconsidered as media bearing the software. As used herein, unlessrestricted to non-transitory, tangible “storage” media, terms such ascomputer or machine “readable medium” refer to any medium thatparticipates in providing instructions to a processor for execution.

Hence, a machine readable medium, such as computer-executable code, maytake many forms, including but not limited to, a tangible storagemedium, a carrier wave medium or physical transmission medium.Non-volatile storage media include, for example, optical or magneticdisks, such as any of the storage devices in any computer(s) or thelike, such as may be used to implement the databases, etc. shown in thedrawings. Volatile storage media include dynamic memory, such as mainmemory of such a computer platform. Tangible transmission media includecoaxial cables; copper wire and fiber optics, including the wires thatcomprise a bus within a computer system. Carrier-wave transmission mediamay take the form of electric or electromagnetic signals, or acoustic orlight waves such as those generated during radio frequency (RF) andinfrared (IR) data communications. Common forms of computer-readablemedia therefore include for example: a floppy disk, a flexible disk,hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD orDVD-ROM, any other optical medium, punch cards paper tape, any otherphysical storage medium with patterns of holes, a RAM, a ROM, a PROM andEPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wavetransporting data or instructions, cables or links transporting such acarrier wave, or any other medium from which a computer may readprogramming code and/or data. Many of these forms of computer readablemedia may be involved in carrying one or more sequences of one or moreinstructions to a processor for execution.

EXAMPLES

The following examples are provided to illustrate various processes,configurations and systems that may be performed with the high powervisible laser source in a 3-D printer system. These examples are forillustrative purposes only and are not intended to limit the scope ofthe present invention.

Turning to FIG. 1 a 3-D printing system is schematically shown, whichincludes a computer system and software for converting a solid modeldirectly to a solid part by using laser sintering to fuse a powdersubstrate layer by layer. The visible laser (1001) in this exampleincludes the laser in FIG. 4 (4000) and the laser plate drawing in FIG.4 (4000) where the visible laser diodes (4001) are high power, highbrightness laser diodes, which output laser light at a wavelength ofabout 450 nm. An aspheric lens (4002) is used to collimate each of thelaser sources and is used during manufacture to align the output beam ofeach laser on the laser plate. The lasers are aligned with the slow axisperpendicular to the laser plate to allow a cylindrical telescope (4003)to be aligned with the slow axis of the laser diode to circularize thedivergence of the beamlet in both the slow and fast axes. Thecylindrical telescope (4003) elements are placed during the manufactureprocess with a pick-and-place machine (e.g., robot), which may be customor provided by one of several manufactures of such machines. Thepick-and-place robot can be capable of placing an optic and orientatingit along 6 axes, as well as applying a UV curing adhesive or thermalepoxy for affixing the optic in place. After placement, the system mayrequire no further alignment after being affixed to the plate with anultraviolet (UV) curable resin. The turning mirrors or prisms (4004) arealso put in place by a pick-and-place machine during manufacture, andmay require no further alignment after being affixed to the plate with aUV curable resin. The output beams from the laser plates are aligned byadjusting the position of the collimating asphere during manufacturingto form a single spot in the far-field which corresponds to the beamletsbeing parallel and highly aligned. In some situations, a final focusingoptic is an asphere to minimize the laser spot and to maximize theuseable aperture of the lens.

The laser plates can be stacked to form a two dimensional beam as shownin FIG. 5 (5000) and interlaced (5002) to form a single beam. The singlebeam formed from the two interlaced arrays can then be combined usingdichroic filters or gratings with the wavelength of the two differentsets of arrays being separated by 2 nm. After the two sets of arrays arecombined in a dichroic filter, a polarizer can be used to combine asimilar set of arrays arranged with their polarization orthogonal to thefirst set of arrays, thereby resulting in 4 arrays being combined withanother 4 arrays to form a beam with an 8× increase in source brightnessusing wavelength and polarization combination. This approach may havefeatures similar to that described in U.S. Pat. No. 5,715,270 to Zedikeret al. (“High efficiency, high power direct diode laser systems andmethods therefor”), which is entirely incorporated herein by reference.The polarization combination can be performed either before formation ofthe composite beam (wavelength combining) or after. The composite beamis then launched into the pump core of a triple clad fiber (4007, FIG.4) with a fused silica core. The high intensity beam in the pump core tocreate gain through the SRS process in both the cladding and the core.However, the core has a laser cavity associated with it (3003 and 3005,FIG. 3) leading to oscillation in the core. A complete model of thelaser using equations for stimulated Raman scattering are used to modelthe behavior of the visible laser diode pumped Raman laser. An exampleequation for stimulated Raman scattering may be found in M. Rini, etal., “Numerical modeling and optimization of Cascaded Raman fiberLasers,” IEEE Journal of Quantum Electron, vol. 36, pp. 117-1122 (2000),which is entirely incorporated herein by reference.

The evolution of the pump power into the single mode output for thiscase is shown in FIG. 6A and FIG. 6B. FIG. 6A shows the forward (6001)propagating and backward (6002) propagating single mode power in a 10 μmcore as a function of the position in the resonator fiber oscillating at460 nm. FIG. 6B shows the forward propagating (6011, 6012) and backwardpropagating (6021, 6022) pump signals in the 85 μm diameter clad as afunction of the position in the resonator fiber. The forward propagatingpumps includes two separate wavelengths at 450 nm (6011) and 452 nm(6012). Similarly, the backward propagating pump includes two separatewavelengths at 450 nm (6021) and 452 nm (6022). The outside clad whichsets the pump clad numerical aperture at 0.49 is 125 μm in diameter. Thesingle transverse mode output power for this example is greater than 2kW using a 30% reflective output coupler (3005).

The laser output can be directly controlled by modulating the pumpdiodes or the laser can be configured as a master oscillator—poweramplifier and the master oscillator can be modulated at high speed.Referring to FIG. 1, the laser beam passes through a pair of x-yscanners (1003) to translate the laser beam across the top of thesubstrate (1007), which is a powder bed in this example. The x-yscanners can be positioned either before or after the focusing objective(1005) depending on the focal length of the lens. The diameter of thespot (1006) that is formed is a function of the diameter of thecollimated beam (1004) and the focal length of the objective lens(1005). A 70 μm diameter spot can be formed by a 158.4 cm focal lengthlens (62.4″) if the input laser beam has a divergence of 44 grad. A beamdivergence of 44 grad corresponds to an input beam diameter (1004) of1.3 cm for a wavelength of 459 nm. This beam diameter is the result of a22.6 cm focal length lens collimating (1002) the single mode output ofthe laser (1001) which is a mode diameter of 10 μm exiting the laser.The result is a system that can be scanned over a plane of 53″×53″ ofthe substrate (1007). Combining this with a large displacement elevator(1008) allows for a build volume of 53″×53″×55″.

The laser can be scanned over a bed of powder to define the part. Thepowder bed is rolled over the part after each layer is scanned and theelevator is decremented by 100 nm, giving a layer resolution of 100 nm.The powder is greater than 10 nm in diameter, greater than 50 nm indiameter but not greater than 100 nm in diameter for this particularexample. The diameter of the powder can affect the surface roughness andthe build speed of the part. The build speed of the part can be greaterthan or equal to about 50 cubic centimeters per hour using a 1 kW laserat 459 nm as shown in Table 2. This is over a factor of 2.5× faster thanan IR laser and a factor of 150× build volume which represents asubstantial improvement over the current technology.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. It is not intendedthat the invention be limited by the specific examples provided withinthe specification. While the invention has been described with referenceto the aforementioned specification, the descriptions and illustrationsof the embodiments herein are not meant to be construed in a limitingsense. Numerous variations, changes, and substitutions will now occur tothose skilled in the art without departing from the invention.Furthermore, it shall be understood that all aspects of the inventionare not limited to the specific depictions, configurations or relativeproportions set forth herein which depend upon a variety of conditionsand variables. It should be understood that various alternatives to theembodiments of the invention described herein may be employed inpracticing the invention. It is therefore contemplated that theinvention shall also cover any such alternatives, modifications,variations or equivalents. It is intended that the following claimsdefine the scope of the invention and that methods and structures withinthe scope of these claims and their equivalents be covered thereby.

What is claimed is:
 1. A printing system for forming a three-dimensionalobject, comprising: a. a laser light source that generates a coherentbeam of visible light by stimulated Raman scattering; b. a substrate inoptical communication with said laser light source; c. a scanning moduledownstream of said laser light source, wherein said scanning module isadapted to generate a scanning motion of said coherent beam of visiblelight with respect to said substrate, which scanning motion correspondsto a predetermined shape of said three-dimensional object; and d. acomputer control system operatively coupled to said laser light sourceand said scanning module, wherein said computer control system isprogrammed to (i) control said scanning motion in a predetermined mannerand (ii) modulate a power of said laser light source, to form saidobject from said substrate.
 2. The printing system of claim 1, whereinsaid scanning module is adapted to (i) move said coherent beam ofvisible light, or (ii) move said substrate relative to said coherentbeam of visible light.
 3. The printing system of claim 1, whereinscanning module comprises one or more galvanometers.
 4. The printingsystem of claim 1, wherein said scanning module comprises at least twoorthogonal linear translation stages that move said substrate withrespect to said coherent beam of visible light.
 5. The printing systemof claim 1, further comprising an objective lens between said laserlight source and said substrate, wherein said objective lens focusessaid coherent beam of visible light onto said substrate.
 6. The printingsystem of claim 5, wherein said objective lens is an f-theta lens. 7.The printing system of claim 5, wherein said objective lens is a shortfocal length lens that generates a sub-micron spot on said substratefrom said coherent beam of visible light.
 8. The printing system ofclaim 1, further comprising a vertical translator that (i) moves saidsubstrate along a direction generally parallel to a direction of saidcoherent beam of visible light, or (ii) moves an assembly comprisingsaid laser light source along a direction generally parallel to adirection of said coherent beam of visible light.
 9. The printing systemof claim 8, wherein said vertical translator moves said substrate orsaid assembly in increments of at least about 10 nanometers.
 10. Theprinting system of claim 1, wherein said laser light source comprisesone or more visible laser diodes.
 11. The printing system of claim 10,wherein an individual diode among said one or more visible laser diodesis an individual laser chip that is bonded to a plate.
 12. The printingsystem of claim 1, wherein said laser light source comprises sets oflaser diodes, wherein each set of said plurality comprises a pluralityof laser diodes, and wherein each set of said plurality generates one ormore coherent light beams that are comprised in said coherent lightbeam.
 13. The printing system of claim 12, further comprising acollimating lens that aligns light beams from each set of said pluralityof laser diodes.
 14. The printing system of claim 13, further comprisinga circularizing optic for making the divergence of light beams from saidcollimating lens symmetric.
 15. The printing system of claim 12, furthercomprising a compressing optical element that compresses light beamsfrom said sets of laser diodes reduce or minimize dead space betweensaid light beams.
 16. The printing system of claim 1, wherein saidcoherent beam of visible light is coherent single mode light.
 17. Theprinting system of claim 1, wherein said laser light source comprises anoptical fiber, and wherein said laser light source generates saidcoherent beam of visible light in said optical fiber with a Rayleighloss that is less than about 50 decibels per kilometer (db/km).
 18. Theprinting system of claim 1, wherein said light source comprises at leastone laser diode and a fiber in optical communication with said laserdiode.
 19. The printing system of claim 18, wherein said fiber comprises(i) a central core that is substantially single mode, (ii) a cladding oflarger diameter than the central core that captures a plurality of beamsof visible light outputted from said laser diode array, and (iii) anouter cladding that guides said beams of visible light outputted by saidlaser diode array along said fiber.
 20. The printing system of claim 19,wherein said central core and said outer cladding are arranged such thatsaid plurality of beams of visible light transverse said central core tocreate gain in the central core through stimulated Raman scattering. 21.The printing system of claim 1, wherein said object is a component of aMicro-Electrical-Mechanical (MEMS) device.
 22. A printing system forforming a three-dimensional object, comprising: a. a laser light sourcethat comprises an optical fiber that outputs a coherent beam of visiblelight in said optical fiber with a Rayleigh loss that is less than about50 decibels per kilometer (db/km); b. a substrate in opticalcommunication with said laser light source; c. a scanning moduledownstream of said laser light source, wherein said scanning module isadapted to generate a predetermined scanning motion of said beam ofvisible light with respect to said substrate, which predeterminedscanning motion corresponds to a shape of said three-dimensional object;and d. a computer control system operatively coupled to said laser lightsource and said scanning module, wherein said computer control system isprogrammed to (i) control said scanning motion in a predetermined mannerand (ii) modulate a power of said laser light source, to form saidobject from said substrate.
 23. The printing system of claim 22, whereinsaid scanning module is adapted to (i) move said coherent beam ofvisible light, or (ii) move said substrate relative to said coherentbeam of visible light.
 24. The printing system of claim 22, whereinscanning module comprises one or more galvanometers.
 25. The printingsystem of claim 22, wherein said scanning module comprises at least twoorthogonal linear translation stages that move said substrate withrespect to said coherent beam of visible light.
 26. The printing systemof claim 22, further comprising an objective lens between said laserlight source and said substrate, wherein said objective lens focusessaid coherent beam of visible light onto said substrate.
 27. Theprinting system of claim 26, wherein said objective lens is an f-thetalens.
 28. The printing system of claim 26, wherein said objective lensis a short focal length lens that generates a sub-micron spot on saidsubstrate from said coherent beam of visible light.
 29. The printingsystem of claim 22, further comprising a vertical translator that (i)moves said substrate along a direction generally parallel to a directionof said coherent beam of visible light, or (ii) moves an assemblycomprising said laser light source along a direction generally parallelto a direction of said coherent beam of visible light.
 30. The printingsystem of claim 29, wherein said vertical translator moves saidsubstrate or said assembly in increments of at least about 10nanometers.
 31. The printing system of claim 22, wherein said laserlight source comprises one or more visible laser diodes.
 32. Theprinting system of claim 31, wherein an individual diode among said oneor more visible laser diodes is an individual laser chip that is bondedto a plate.
 33. The printing system of claim 22, wherein said laserlight source comprises sets of laser diodes, wherein each set of saidplurality comprises a plurality of laser diodes, and wherein each set ofsaid plurality generates one or more coherent light beams that arecomprised in said coherent light beam.
 34. The printing system of claim33, further comprising a collimating lens that aligns light beams fromeach set of said plurality of laser diodes.
 35. The printing system ofclaim 34, further comprising a circularizing optic for making thedivergence of light beams from said collimating lens symmetric.
 36. Theprinting system of claim 33, further comprising a compressing opticalelement that compresses light beams from said sets of laser diodesreduce or minimize dead space between said light beams.
 37. The printingsystem of claim 22, wherein said coherent beam of visible light iscoherent single mode light.
 38. The printing system of claim 22, whereinsaid light source comprises at least one laser diode and a fiber inoptical communication with said laser diode.
 39. The printing system ofclaim 38, wherein said fiber comprises (i) a central core that issubstantially single mode, (ii) a cladding of larger diameter than thecentral core that captures said plurality of beams of visible lightoutputted from said laser diode arrays, and (iii) an outer cladding thatguides said coherent beam of visible light outputted by said laser diodearray along said fiber.
 40. A method for forming a three-dimensionalobject, comprising: a. providing a laser light source and a scanningmodule optically downstream of said laser light source; b. using saidlaser light source, generating a coherent beam of visible light bystimulated Raman scattering; c. directing said coherent beam of visiblelight to a substrate that is in optical communication with said laserlight source; d. generating a feature in or from said substrate, whichfeature corresponds to at least a portion of a predetermined shape ofsaid three-dimensional object; e. using said scanning module, generatinga scanning motion of said coherent beam of visible light with respect tosaid substrate, which scanning motion corresponds to said predeterminedshape of said three-dimensional object; and f. moving said substraterelative to said laser light source along a direction that is generallyparallel to said coherent beam of visible light.
 41. The method of claim40, wherein (e) comprises modulating a power of said laser light source.42. The method of claim 41, wherein said power is modulated at afrequency of at least about 50 kHz.
 43. The method of claim 40, furtherprogramming said scanning motion in memory, which scanning motion isdetermined from a three-dimensional shape of said object.
 44. The methodof claim 40, wherein said feature has a surface roughness from about 0.1nanometers (nm) and 50 nm as measured by transmission electronmicroscopy.
 45. The method of claim 40, wherein in (f), said substrateis moved at a distance of at least about 10 nanometers.
 46. The methodof claim 40, wherein in (f), (i) said substrate is moved along adirection generally parallel to a direction of said coherent beam ofvisible light, or (ii) an assembly comprising said laser light source ismoved along a direction generally parallel to a direction of saidcoherent beam of visible light.
 47. The method of claim 40, wherein saidsubstrate is powder.
 48. The method of claim 47, further comprisingreplenishing said powder subsequent to (d).